Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 4 - Quadratic Functions - 4.6 Solving Quadratic Equations by Using the Quadratic Formula - 4.6 Exercises: 23

Answer

$a=-5,3$

Work Step by Step

First, put all the terms on the left side. Then, to factor by trial and error, determine the two numbers that, when multiplied, equal the third term, and, when added, equal the coefficient of the middle term. $a^2+2a=15$ $a^2+2a-15=0$ $(a+5)(a-3)=0$ $a+5=0$ $a=-5$ or $a-3=0$ $a=3$. So $a=-5,3$.
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